【发布时间】：2022-12-21 02:29:21
【问题描述】：
我有一个链接，我可以通过 DM 获取最小复制示例！
录制视频
对于录制，AVCaptureConnection 为 AVCaptureSession，我在使用前置摄像头时将 isVideoMirrored 设置为 true，在使用后置摄像头时设置为 false。全部为纵向。
保存影片
当我保存视频时，我执行AVAssetExportSession。如果我使用前置摄像头，我想保持isVideoMirrored = true，所以我创建了一个AVMutableComposition来将AVAsset视频轨道的preferredTransform设置为CGAffineTransform(scaleX: -1.0, y: 1.0).rotated(by: CGFloat(Double.pi/2))。对于后置摄像头，我导出 AVAsset 作为输出。
我的部分保存代码：
if didCaptureWithFrontCamera {
let composition = AVMutableComposition()
let assetVideoTrack = asset.tracks(withMediaType: .video).last!
let assetAudioTrack = asset.tracks(withMediaType: .audio).last!
let compositionVideoTrack = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))
let compositionAudioTrack = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: CMPersistentTrackID(kCMPersistentTrackID_Invalid))
try? compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: asset.duration), of: assetVideoTrack, at: CMTime.zero)
try? compositionAudioTrack?.insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: asset.duration), of: assetAudioTrack, at: CMTime.zero)
compositionVideoTrack?.preferredTransform = CGAffineTransform(scaleX: -1.0, y: 1.0).rotated(by: CGFloat(Double.pi/2))
guard let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPreset1280x720) else {
handler(nil)
return
}
exportSession.outputURL = outputURL
exportSession.outputFileType = .mp4
exportSession.shouldOptimizeForNetworkUse = true
exportSession.exportAsynchronously { handler(exportSession) }
} else {
guard let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPreset1280x720) else {
handler(nil)
return
}
exportSession.outputURL = outputURL
exportSession.outputFileType = .mp4
exportSession.shouldOptimizeForNetworkUse = true
exportSession.exportAsynchronously { handler(exportSession) }
}
合并视频
稍后，为了查看保存的视频，我想将它们合并为一个视频，并通过 AVMutableComposition 保持每个视频的原始方向。
部分起作用的是将 AVMutableComposition 的视频轨道设置为单个 AVAsset 视频的视频轨道的 preferredTransform 属性。唯一的问题是单一方向应用于所有视频（即镜像不应用于后置摄像头录制的视频，同样适用于前置摄像头视频）。
从我遇到的解决方案来看，我似乎需要申请AVMutableVideoCompositionInstruction，但在尝试这样做时，AVAssetExportSession 似乎根本没有考虑videoComposition 说明。
任何指导都是极其感谢，因为我一生都无法解决它......
我尝试的合并代码：
func merge(videos: [AVURLAsset], for date: Date, completion: @escaping (_ url: URL, _ asset: AVAssetExportSession)->()) {
let videoComposition = AVMutableComposition()
var lastTime: CMTime = .zero
var count = 0
var instructions = [AVMutableVideoCompositionInstruction]()
let renderSize = CGSize(width: 720, height: 1280)
guard let videoCompositionTrack = videoComposition.addMutableTrack(withMediaType: .video, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }
guard let audioCompositionTrack = videoComposition.addMutableTrack(withMediaType: .audio, preferredTrackID: Int32(kCMPersistentTrackID_Invalid)) else { return }
for video in videos {
if let videoTrack = video.tracks(withMediaType: .video)[safe: 0] {
//this is the only thing that seems to work, but work not in the way i'd hope where each video keeps its original orientation
//videoCompositionTrack.preferredTransform = videoTrack.preferredTransform
if let audioTrack = video.tracks(withMediaType: .audio)[safe: 0] {
do {
try videoCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: videoTrack, at: lastTime)
try audioCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: audioTrack, at: lastTime)
let layerInstruction = videoCompositionInstruction(videoTrack, asset: video, count: count)
let videoCompositionInstruction = AVMutableVideoCompositionInstruction()
videoCompositionInstruction.timeRange = CMTimeRangeMake(start: lastTime, duration: video.duration)
videoCompositionInstruction.layerInstructions = [layerInstruction]
instructions.append(videoCompositionInstruction)
} catch {
return
}
lastTime = CMTimeAdd(lastTime, video.duration)
count += 1
} else {
do {
try videoCompositionTrack.insertTimeRange(CMTimeRangeMake(start: .zero, duration: video.duration), of: videoTrack, at: lastTime)
let layerInstruction = videoCompositionInstruction(videoTrack, asset: video, count: count)
let videoCompositionInstruction = AVMutableVideoCompositionInstruction()
videoCompositionInstruction.timeRange = CMTimeRangeMake(start: lastTime, duration: video.duration)
videoCompositionInstruction.layerInstructions = [layerInstruction]
instructions.append(videoCompositionInstruction)
} catch {
return
}
lastTime = CMTimeAdd(lastTime, video.duration)
count += 1
}
}
}
let mutableVideoComposition = AVMutableVideoComposition()
mutableVideoComposition.instructions = instructions
mutableVideoComposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
mutableVideoComposition.renderSize = renderSize
dateFormatter.dateStyle = .long
dateFormatter.timeStyle = .short
let date = dateFormatter.string(from: date)
let mergedURL = NSURL.fileURL(withPath: NSTemporaryDirectory() + "merged-\(date)" + ".mp4")
guard let exporter = AVAssetExportSession(asset: videoComposition, presetName: AVAssetExportPresetHighestQuality) else { return }
exporter.outputURL = mergedURL
exporter.outputFileType = .mp4
exporter.videoComposition = mutableVideoComposition
exporter.shouldOptimizeForNetworkUse = true
completion(mergedURL, exporter)
}
func videoCompositionInstruction(_ firstTrack: AVAssetTrack, asset: AVAsset, count: Int) -> AVMutableVideoCompositionLayerInstruction {
let renderSize = CGSize(width: 720, height: 1280)
let instruction = AVMutableVideoCompositionLayerInstruction(assetTrack: firstTrack)
let assetTrack = asset.tracks(withMediaType: .video)[0]
let t = assetTrack.fixedPreferredTransform // new transform fix
let assetInfo = orientationFromTransform(t)
if assetInfo.isPortrait {
let scaleToFitRatio = renderSize.width / assetTrack.naturalSize.height
let scaleFactor = CGAffineTransform(scaleX: scaleToFitRatio, y: scaleToFitRatio)
var finalTransform = assetTrack.fixedPreferredTransform.concatenating(scaleFactor)
if assetInfo.orientation == .rightMirrored || assetInfo.orientation == .leftMirrored {
finalTransform = finalTransform.translatedBy(x: -t.ty, y: 0)
}
instruction.setTransform(t, at: CMTime.zero)
} else {
let renderRect = CGRect(x: 0, y: 0, width: renderSize.width, height: renderSize.height)
let videoRect = CGRect(origin: .zero, size: assetTrack.naturalSize).applying(assetTrack.fixedPreferredTransform)
let scale = renderRect.width / videoRect.width
let transform = CGAffineTransform(scaleX: renderRect.width / videoRect.width, y: (videoRect.height * scale) / assetTrack.naturalSize.height)
let translate = CGAffineTransform(translationX: .zero, y: ((renderSize.height - (videoRect.height * scale))) / 2)
instruction.setTransform(assetTrack.fixedPreferredTransform.concatenating(transform).concatenating(translate), at: .zero)
}
if count == 0 {
instruction.setOpacity(0.0, at: asset.duration)
}
return instruction
}
func orientationFromTransform(_ transform: CGAffineTransform) -> (orientation: UIImage.Orientation, isPortrait: Bool) {
var assetOrientation = UIImage.Orientation.up
var isPortrait = false
if transform.a == 0 && transform.b == 1.0 && transform.c == -1.0 && transform.d == 0 {
assetOrientation = .right
isPortrait = true
} else if transform.a == 0 && transform.b == 1.0 && transform.c == 1.0 && transform.d == 0 {
assetOrientation = .rightMirrored
isPortrait = true
} else if transform.a == 0 && transform.b == -1.0 && transform.c == 1.0 && transform.d == 0 {
assetOrientation = .left
isPortrait = true
} else if transform.a == 0 && transform.b == -1.0 && transform.c == -1.0 && transform.d == 0 {
assetOrientation = .leftMirrored
isPortrait = true
} else if transform.a == 1.0 && transform.b == 0 && transform.c == 0 && transform.d == 1.0 {
assetOrientation = .up
} else if transform.a == -1.0 && transform.b == 0 && transform.c == 0 && transform.d == -1.0 {
assetOrientation = .down
}
return (assetOrientation, isPortrait)
}
extension AVAssetTrack {
var fixedPreferredTransform: CGAffineTransform {
var t = preferredTransform
switch(t.a, t.b, t.c, t.d) {
case (1, 0, 0, 1):
t.tx = 0
t.ty = 0
case (1, 0, 0, -1):
t.tx = 0
t.ty = naturalSize.height
case (-1, 0, 0, 1):
t.tx = naturalSize.width
t.ty = 0
case (-1, 0, 0, -1):
t.tx = naturalSize.width
t.ty = naturalSize.height
case (0, -1, 1, 0):
t.tx = 0
t.ty = naturalSize.width
case (0, 1, -1, 0):
t.tx = naturalSize.height
t.ty = 0
case (0, 1, 1, 0):
t.tx = 0
t.ty = 0
case (0, -1, -1, 0):
t.tx = naturalSize.height
t.ty = naturalSize.width
default:
break
}
return t
}
}
【问题讨论】：
标签： ios swift avcapturesession cgaffinetransform avmutablecomposition